1. Field of the Invention
The present invention relates to computer controlled engine analyzer apparatus for testing multi-cylinder internal combustion engines. In particular, the present invention relates to apparatus for keeping track of cylinder number in a computer-controlled engine analyzer.
2. Description of the Prior Art
With the advent of low-cost microelectronic devices, and in particular microprocessors, digital electronic systems have found increasing use in a wide variety of applications. Digital electronic systems have many significant advantages over analog systems, including increased ability to analyze and store data, higher accuracy, greater flexibility in design and application, and the ability to interface with computers having larger and more sophisticated data processing and storage capabilities. In the past, some engine analyzer systems for performing tests on multi-cylinder internal combustion engines have been proposed which utilize microprocessors and digital circuitry to control some of the functions of the engine analyzer apparatus.
In any multi-function engine analyzer, there is a need to keep track of the current cylinder number so that engine tests such as displaying primary and secondary ignition waveforms, power checking and engine timing measurements can be performed. U.S. Pat. No. 3,572,103 by J. Marino shows one arrangement used in the prior art for keeping track of the cylinder number. In this patent, a ring counter driven by pulses from the ignition system maintains the cylinder count. The number of stages of the ring counter is selectable by a cylinder selector switch. The operator sets the selector switch to the proper number of cylinders, and the selector switch in turn enables the necessary stages of the ring counter.